JP5028080B2 - Low wear sliding member and artificial joint using the same - Google Patents

Description

  The present invention relates to a low-abrasion sliding member used in a wet environment, and more particularly to a sliding member used for an artificial joint for prosthetic human joints.

  As a sliding member constituting a sliding surface of an artificial joint such as an artificial hip joint or an artificial knee joint, ultra high molecular weight polyethylene (referred to as UHMWPE) is generally used. However, when artificial joints are used in vivo, UHMWPE wear debris caused by frictional motion can induce bone osteolysis. A decrease in the adhesion between the artificial joint and the bone caused by bone melting, so-called loosening, is a major complication of artificial joint replacement. The normal wear amount of UHMWPE is about 0.1 mm to 0.2 mm per year. After artificial joint replacement, there is no problem for a while, but loosening becomes significant after about 5 years, so the artificial joint is replaced. There is a need and a great burden on the patient.

  One solution to loosening is to reduce the amount of UHMWPE wear debris. For this purpose, various attempts have been made, such as a combination of materials for joint surfaces and improvement of the materials themselves. As one of them, in recent years, research on UHMWPE (cross-linked polyethylene, hereinafter referred to as CLPE) in which molecular chains are cross-linked by irradiation with electron beams or gamma rays has been actively conducted (for example, Patent Documents 1 to 3). ). These studies take advantage of the fact that when a polymer material is irradiated with high-energy radiation such as gamma rays or electron beams, free radicals are generated by molecular chain scission, followed by recombination of molecular chains and cross-linking reactions. ing. The aforementioned CLPE is superior in wear resistance characteristics compared to conventional UHMWPE, and it is reported that the amount of wear can be reduced to 1/5 to 1/10.

  In addition, active research has been conducted to improve the sliding characteristics of the sliding surface by forming a coating layer on the surface of UHMWPE. For example, a film of a random copolymer having allylamine and phosphorylcholine-like groups is fixed on the surface of a medical device that requires excellent sliding characteristics such as an artificial joint, and the biocompatibility and surface lubricity. Is known to be given (for example, Patent Document 4).

In particular, grafting a polymerizable monomer having a phosphorylcholine group to the sliding surface of an artificial joint made of UHMWPE has a high effect of suppressing wear of the artificial joint, and is made of a polymer material that can suppress the generation of wear powder than before. An artificial joint member is obtained (for example, Patent Document 5).
Japanese Patent No. 2984203 US Pat. No. 6,228,900 International Publication No. 97/29793 Pamphlet International Publication No. 01/05855 Pamphlet JP 2003-310649 A

With the current technology, even if the sliding surface of the joint sliding member is modified to give wear resistance, the sliding surface cannot be completely prevented from being worn. Therefore, even if the conventional surface-modified joint sliding member shows good wear resistance immediately after the start of use, if the surface-modified region is removed by abrasion or peeling after long-term use, the wear resistance Will deteriorate at once. If wear powder is generated due to a decrease in wear resistance, there is a high possibility of loosening.
Since the above-mentioned joint sliding member using CLPE has a short clinical use period, it has not been sufficiently confirmed whether the wear resistance can be maintained for a long period of time.

In addition, when a technique for fixing a random copolymer film on the surface of a medical device made by UHMWPE is applied to an artificial joint sliding member, the random copolymer film is placed under the severe friction and wear environment of UHMWPE. Possibility of peeling from the surface is extremely high, and practical application is difficult.
The reason why such peeling occurs is that the bonding strength between the UHMWPE surface and the random copolymer film is low. The reason why the bond strength is low is that a sufficiently copolymerized random copolymer film is fixed on the surface of UHMWPE, and another cause is that the polymerized random copolymer film and The functional group for bonding does not exist.

On the other hand, in Patent Document 5, the bonding force between the polymer chain having a phosphorylcholine group and the UHMWPE surface is increased by graft-bonding the polymer chain having a phosphorylcholine group to the surface of the UHMWPE substrate. Successful. Thereby, the joint sliding member which formed the abrasion-resistant film | membrane which does not peel in a severe friction wear environment on the sliding surface of UHMWPE was obtained. However, it has not been fully confirmed whether the joint sliding member can maintain the abrasion resistance for a long period of time. For example, in Patent Document 5, a stainless steel ball is brought into contact with the sliding surface of the obtained joint sliding member in a loaded state, and an acceleration test of wear resistance up to 3 million rotation cycles is performed. This corresponds to the use for 3 years, and it is impossible to know the wear resistance when used for a long period (for example, 5 years or more) required for an artificial joint.

  Then, an object of this invention is to provide the sliding member which can maintain abrasion resistance over a long period of time, and was excellent in durability, and its manufacturing method.

As a result of diligent research, the present inventors have found that when a polymer film having a phosphorylcholine group is fixed on the surface of UHMWPE, the wear resistance depends on the thickness of the polymer film and the optimum range exists. This completes the sliding member for an artificial joint of the present invention.
That is, the sliding member of the present invention is
A low-abrasion sliding member used in a wet environment,
The sliding member includes a base material molded from a polymer material having a methylene group, and a polymer film covering the sliding surface of the base material,
The polymer film is composed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface,
The polymer film has a thickness of 10 to 200 nm;
The phosphoric acid index (the peak intensity of the phosphate group / the peak intensity of the methylene group in the infrared spectroscopic analysis spectrum) of the sliding surface is 0.45 or more.

  The sliding member of the present invention can suppress the amount of wear even if it is used in a severe friction environment for a long period of time, so that bone melting induced by wear powder hardly occurs. Further, since the shape of the sliding surface hardly changes over a long period of time, the performance of the artificial joint at the time of design can be maintained. As a result, once the replacement of the artificial joint is performed, the artificial joint functions stably over a long period of time, so that the number of revisions can be reduced or eliminated. Further, even in a moist environment other than the internal environment, it exhibits excellent wear resistance, and is therefore suitable for a sliding member placed in a friction environment.

  Further, the present invention is a method for producing the above sliding member, the step of forming a base material made of a polymer material having a methylene group, and a phosphorylcholine group on the sliding surface of the base material. Forming a polymer film on the sliding surface by fixing the polymer chain having a graft bond, and the step of forming the polymer film starts photopolymerization on the sliding surface of the substrate. And irradiating the sliding surface of the substrate with ultraviolet light having an intensity required to excite the photopolymerization initiator while being immersed in a solution containing a polymerizable monomer having a phosphorylcholine group. And the monomer concentration of the solution containing the polysynthetic monomer is 0.25 to 0.50 mol / L.

  According to the present invention, a uniform polymer film having a preferable film thickness can be formed by adjusting the monomer concentration.

  According to the sliding member of the present invention, it is possible to provide a sliding member that can maintain wear resistance for a long period of time and has excellent durability.

<Embodiment 1>
FIG. 1 is a schematic view of an artificial hip joint 1 which is a kind of artificial joint. The artificial hip joint 1 includes a sliding member (acetabular cup) 10 that is fixed to the acetabulum 94 of the hipbone 93 and a femoral stem 20 that is fixed to the proximal end of the femur 91. The acetabular cup 10 has a cup base 12 having a substantially hemispherical acetabular fixation surface 14 and a sliding surface 16 recessed in a substantially hemispherical shape, and a polymer film 30 coated on the sliding surface 16. ing. By fitting and sliding the head 22 of the femoral stem 20 on the sliding surface 16 of the acetabular cup 10, it functions as a hip joint.

  As shown in FIGS. 1 and 2, the acetabular cup 10 of the present invention has a surface of the sliding surface 16 of the cup base 12 covered with a polymer film 30 having a phosphorylcholine group. Specifically, the polymer film 30 has a structure in which polymer chains having phosphorylcholine groups are arranged on the surface. Such a structure is similar to the structure of a biological membrane.

  A biological membrane constituting the surface of an aggregate such as a living joint portion is an aggregate of phospholipid molecules, and the surface is microscopically covered with a phosphorylcholine group (Ishihara: Surgical, Vol. 61, p. 132 (1999)). This biological membrane forms a lubricated joint surface with a very low friction coefficient by holding a lubricating liquid inside the membrane. The polymer membrane 30 of the present invention also has a high affinity with the lubricating liquid like the biological membrane and can hold the lubricating liquid inside the membrane, so that it is compared with the sliding surface 16 of the conventional acetabular cup 10. And the coefficient of friction can be lowered.

  As described above, if the sliding surface 16 of the acetabular cup 10 is coated with the polymer film 30 having a phosphorylcholine group, the sliding characteristics can be improved and the wear resistance can be improved. However, sliding members for artificial joints must be able to maintain wear resistance over a long period of time in a harsh environment where they slide while supporting the overall weight in contact with body fluids, that is, they must have extremely strict durability. Is done.

Therefore, in the present invention, the relationship between the durability of the acetabular cup 10 and the film thickness of the polymer film 30 was examined. As a result, it was found that excellent wear resistance was exhibited when the thickness of the polymer film 30 was 10 to 200 nm. If the film thickness is less than 10 nm, the wear resistance is insufficient and the durability deteriorates in a short period, which is not preferable. Also, when is larger than 200nm thickness, tended to decrease uniformity of the polymer layer 30, partially coating occurs is thin or peel film portion without a polymer film 30 from the portion peeling Or the acetabular cup 10 is worn and wear resistance is lowered, which is not preferable. A particularly preferable film thickness of the polymer film 30 is 30 to 100 nm.
When the durability of the acetabular cup 10 is increased, generation of wear powder can be suppressed over a long period of time, so that loosening is suppressed. Therefore, it is possible to provide an artificial joint that requires little or no re-replacement.

In the present invention, attention is also paid to the density of the polymer film 30 in order to extend the durability of the acetabular cup 10. In the present invention, the “density” of the polymer film is strictly the amount of MPC polymer present per unit area, but when the MPC polymer film thickness is sufficiently thin, the MPC polymer per unit area Can be used as an indicator of congestion. Therefore, it can be considered that the higher the density, the denser the MPC polymer is on the sliding surface of the acetabular cup.
In the present invention, a new concept of “phosphoric acid index” is introduced as a unit for defining the density of the polymer film 30 to quantitatively define the durability and the density of the polymer film.
Here, the "phosphoric acid index", in the spectrum of the Fourier transform infrared spectroscopy (FT-IR) analysis, of 1080 cm ^-1 is the absorption of the phosphate group to the peak intensity I _methylene 1460 cm ^-1 is the absorption of the methylene group the intensity ratio of the peak intensity I _phosphate, that is defined as I _phosphate / I _methylene.

  When a polymer film 30 having a phosphorylcholine group is formed on a cup base material 12 made of a polymer material containing a methylene group and FT-IR measurement is performed as in the present invention, the methylene group resulting from the cup base material 12 is obtained. And a phosphate group peak attributable to the polymer film 30 are observed. At this time, if the cup substrate 12 is constant and the film thickness of the polymer film 30 does not change extremely (for example, if the film thickness difference is within 1 μm), the phosphate index calculated from these two peak intensities Is substantially proportional to the number of phosphate groups present per unit area of the cup base 12.

Using this phosphoric acid index, the durability of the mortar cup 10 provided with the polymer film 30 having a phosphorylcholine group on the sliding surface 16 was examined. In the polymer film 30 having a film thickness of 10 to 200 nm, phosphorus If the acetabular cup has an acid index of 0.32 or more, the durability is remarkably improved as compared to the conventional acetabular cup, and the experimental results show that the accelerated experiment has a durability of 5 years or more. Obtained. Furthermore, an experimental result has been obtained that the acetabular cup having a phosphate index of 0.45 or more has a durability of 10 years or more. This is the case when artificial joint replacement is performed after reaching a certain age. It can be said that this is equivalent to the number of years that do not require re-substitution throughout life.
Thus, in order to improve the durability of the acetabular cup 10, the phosphoric acid index of the polymer film 30 is preferably 0.32 or more, and more preferably 0.45 or more.

  Further, when the polymer film 30 is highly hydrophilic, it is considered that the polymer film 30 becomes compatible with the lubricating liquid in the body. The polymer film 30 sufficiently wetted by the lubricating liquid is expected to impart excellent slidability to the sliding surface 16 of the acetabular cup 10 and enhance the durability of the acetabular cup 10. This hydrophilicity can be changed depending on the density of the polymer film 30. Therefore, in the present invention, the relationship between the phosphate index and hydrophilicity, and the relationship between durability and hydrophilicity were clarified. The hydrophilic property (wetting property with respect to water) is defined by a contact angle when water is dropped on the polymer film 30.

When the phosphoric acid index increases, the polymer film 30 having a phosphorylcholine group tends to have improved hydrophilicity (wetting property) and a smaller water contact angle. However, when the phosphoric acid index was 0.3 or more, the contact angle was saturated at 14 °, and even if the phosphoric acid index was further increased, the contact angle did not decrease.
As for the durability, in the acetabular cup 10 estimated to have a durability of 5 years or more, which is a sufficient number of years as a clinical use period, from the result of the acceleration experiment, the polymer film 30 is wet with water. In the acetabular cup 10 that is estimated to have a long-term durability of 10 years or more with a contact angle of 20 ° or less, the polymer film 30 has a contact angle of 14 at a saturation angle. ° or less. Thus, the contact angle of the polymer film 30 with respect to water is preferably 20 ° or less, more preferably 14 ° or less, and the durability of the acetabular cup is enhanced to suppress generation of wear powder over a long period of time. As a result, loosening can be suppressed, and an artificial joint with less or unnecessary re-replacement can be obtained.

  In order to manufacture the sliding member of the present invention, it is necessary to fix the polymer film 30 to the sliding surface 16 of the mortar cup 10. Several fixing methods are conventionally known. In the present invention, the polymer film 30 is fixed by bonding a polymerizable monomer having a phosphorylcholine group to the sliding surface 16 by graft polymerization using ultraviolet rays. Yes. In this method, only the sliding surface 16 can be modified without deteriorating the performance such as the strength of the polymer material constituting the acetabular cup 10, the bonding portion is chemically stable, and a large amount There is an advantage that the density of the polymer film 30 can be increased by forming the phosphorylcholine group on the sliding surface of the artificial joint member.

For the formation of the polymer film 30, a polymerizable monomer having a phosphorylcholine group is used, and in particular, a phosphorylcholine group at one end and a functional group capable of graft polymerization with the polymer material constituting the acetabular cup 10 at the other end. By selecting the monomer, the polymer film 30 can be grafted to the sliding surface 16 of the acetabular cup 10.
Suitable polymerizable monomers for the present invention include, for example, 2-methacryloyloxyethyl phosphorylcholine, 2-acryloyloxyethyl phosphorylcholine, 4-methacryloyloxybutylphosphorylcholine, 6-methacryloyloxyhexylphosphorylcholine, ω-methacryloyloxyethylene phosphorylcholine, 4- And styryloxybutyl phosphorylcholine. In particular, 2-methacryloyloxyethyl phosphorylcholine (referred to as MPC) is preferable.

  The MPC monomer has a chemical structural formula as shown below, and includes a phosphorylcholine group and a polymerizable methacrylic acid unit. The MPC monomer is characterized in that it can easily form a high molecular weight MPC polymer by radical polymerization (Ishihara et al .: Polymer Journal, Vol. 22, p. 355 (1990)). Therefore, when the polymer film 30 is synthesized from the MPC monomer, the graft bonding between the polymer film 30 and the sliding surface 16 can be performed under relatively mild conditions, and the polymer film 30 having a high density is formed. A large amount of phosphorylcholine groups can be formed on the sliding surface 16.

  The polymer film 30 that can be used in the present invention is not only a homopolymer composed of a single polymerizable monomer having a phosphorylcholine group, but also a copolymer composed of a monomer having a phosphorylcholine group and, for example, another vinyl compound monomer. It can also be formed from a polymer. Thereby, functions such as improvement of mechanical strength can be added to the polymer film 30.

  The cup base 12 of the acetabular cup 10 is molded from a polymer material having a methylene group, but UHMWPE is preferably used. UHMWPE is suitable for the cup base material 12 because it is excellent in mechanical properties such as wear resistance and deformation resistance among polymer materials having a methylene group. Since UHMWPE has higher wear resistance as the molecular weight increases, it is preferable to use UHMWPE having a molecular weight of at least 1 million g / mol, preferably at least 3 million g / mol.

Furthermore, CLPE obtained by crosslinking UHMWPE is more excellent in mechanical properties than UHMWPE, and therefore can be preferably used for the cup base 12 of the acetabular cup 10. The cup base material 12 made of CLPE can be obtained by forming a cup shape after irradiating UHMWPE with a high energy ray such as X-ray irradiation, gamma ray irradiation, or electron beam irradiation and crosslinking treatment. Cross-linking treatment of CLPE can also be performed using a cross-linking agent instead of high energy rays , but should be used when the biosafety of the cross-linking agent is uncertain when used for biomaterials such as artificial joints. I can't. Compared to this, a crosslinking treatment with high energy rays is preferable because the crosslinking treatment can be performed without impairing the biosafety of UHMWPE.

  In particular, the CLPE cup base material 12 preferably contains free radicals produced when irradiated with high energy rays such as X-rays, gamma rays, or electron beams. Since the free radicals contained in the cup base 12 can function as a starting point of polymerization when a polymerizable monomer is graft-polymerized on the sliding face 16 of the cup base 12, This is effective for increasing the density of the molecular film 30. However, since the modification of the entire cup base 12 to CLPE leads to an increase in cost, for example, only the sliding surface 16 of the cup base 12 is modified to CLPE by a crosslinking treatment, so that the wear resistance of the sliding surface 16 is increased. The cup base 12 having improved properties is also suitable for the mortar cup 10.

In order to obtain such a radical-containing CLPE cup base material 12, a step of preparing a polymer material having a methylene group irradiated with high energy rays in advance is performed before the step of molding the cup base material 12. Good. The step of preparing the polymer material includes a process of irradiating the polymer material having a methylene group with gamma rays and a process of heat-treating the polymer material irradiated with gamma rays at a temperature lower than its melting point. UHMWPE cup base material 12 is irradiated with high energy rays to generate a large amount of free radicals, and then heat-treated at a melting point or lower, consuming most of the free radicals to CC recombination and cross-linking, A portion can be left in the cup substrate 12. It is not preferable to set the treatment temperature in the heat treatment process to a melting point or higher because almost all free radicals are consumed.

  The acetabular cup 10 for an artificial hip joint according to this embodiment is formed by molding a cup base material 12 by machining or the like of a polymer material having a methylene group (for example, UHMWPE). It can manufacture by graft-bonding the polymer film 30 which has this. Here, in order to graft-bond the polymer film 30 to the sliding surface 16 of the cup base 12, a photopolymerization initiator is applied to the sliding surface 16 of the cup base 12, and the cup base 12 is Then, it is immersed in a solution containing a polymerizable monomer having a phosphorylcholine group, and in this state, the sliding surface 16 of the cup base 12 is irradiated with ultraviolet rays (for example, a wavelength of 300 to 400 nm). When the sliding surface 16 of the cup base 12 is irradiated with ultraviolet rays, the polymerizable monomer in the vicinity of the sliding surface 16 is polymerized to form the polymer film 30, and the polymer film 30 is grafted to the sliding surface 16. .

The film thickness of the resulting polymer film 30 depends on the monomer concentration of the solution containing the polymerizable monomer, the temperature of the solution, the irradiation time of the ultraviolet rays, and the amount of free radicals contained in the cup substrate 12, and adjusts them. Thus, the polymer film 30 having a desired film thickness can be obtained. The ultraviolet irradiation time is preferably 40 minutes or longer. Here, when the polymer film 30 is formed under the conditions of the solution concentration (0.5 mol / L) and the solution temperature (60 ° C.) disclosed in the example of Patent Document 5, the ultraviolet irradiation time is set to Up to 40 minutes, the increasing rate of the phosphoric acid index of the polymer film 30 formed on the sliding surface 16 of the acetabular cup 10 is high. Therefore, the ultraviolet irradiation time is preferably 40 minutes or more , more preferably 45 minutes to 90 minutes .

  In order to make the film thickness of the polymer film 30 10 to 200 nm when the irradiation time is 40 minutes, the monomer concentration of the solution is preferably adjusted to 0.25 mol / L to 0.5 mol / L. When the monomer concentration is lower than 0.25 mol / L, not only the film thickness of the polymer film 30 becomes too thin, but also the density of the polymer film 30 on the sliding surface 16 of the acetabular cup 10 is preferably reduced. Absent. On the other hand, when the monomer concentration is higher than 0.5 mol / L, the monomers are polymerized while floating in the solution before reaching the sliding surface 16 of the acetabular cup 10 and graft polymerization. When such polymerization occurs, the monomer concentration locally decreases, and the film thickness of the polymer film 30 does not increase. On the other hand, since the monomer is sufficiently present in other portions, the film thickness of the polymer film 30 increases. As a result, the polymer film 30 with uneven thickness is formed, and the polymer film 30 with low durability is formed. Therefore, it is not preferable that the monomer concentration is higher than 0.5 mol / L.

<Embodiment 2>
FIG. 3 shows a bipolar hip prosthesis 40, which is another hip prosthesis. The artificial hip joint 40 is characterized by a bone head portion, and is composed of two members, a ball-shaped bone head 22 and an outer head 42 that receives the bone head 22.
The bone head 22 is made of a ceramic or metal ball-shaped member, and is fixed to the proximal portion of the stem body 21.
The outer head 42 includes an outer shell 44 that is a semispherical hollow member made of metal or ceramics, a liner base 46 made of UHMWPE fixed inside the outer shell 44, and a spherical slide inside the liner base 46. The polymer film 30 is fixed to the moving surface 16. The liner base material 46 and the polymer film 30 constitute a sliding member for an artificial joint. The polymer film 30 contains a phosphorylcholine group graft-bonded to the sliding surface 16 as in the first embodiment. It is formed from a polymer chain.
The outer head 42 slidably receives the bone head 22 on the sliding surface 16 of the liner base 46 and constitutes a first sliding portion. Further, the outer head 42 itself is slidably received by the acetabulum of the living bone, and constitutes the second sliding portion.

  The bipolar hip prosthesis 40 is configured to sequentially slide at the first and second sliding portions according to the amount of movement of the hip joint. First, when the first sliding motion occurs in the first sliding portion and the amount of motion of the hip joint exceeds the movable range of the first sliding portion, the second sliding motion occurs in the second sliding portion. Therefore, in the range of daily life, the first sliding motion is the main, and the wear amount of the first sliding portion tends to be large. In the present embodiment, the sliding surface 16 of the liner base 46 of the outer head 42 is provided with the polymer film 30 having a phosphorylcholine group, so that the sliding characteristics of the first sliding portion are improved and the wear resistance is increased. Improve the durability and durability. Thereby, generation | occurrence | production of an abrasion powder can be suppressed over a long period of time, loosening can be suppressed, and an artificial hip joint with few or unnecessary re-replacements can be obtained.

<Embodiment 3>
FIG. 4 shows an artificial shoulder joint 70, which is composed of a sliding member (glenoid cup 15) fixed to the glenoid of the scapula and a humeral stem 25 fixed to the proximal end of the humerus. Has been.
The humeral stem 25 is composed of a stem body 26 inserted into the bone marrow of the humerus and a substantially hemispherical metal or ceramic bone head 27 fixed to the proximal end of the stem body 26. .
The glenoid cup 15 includes a cup base 17 having a scapula stem 19 buried in the glenoid of the scapula, a shallow dish-shaped sliding surface 16, and a polymer coated on the sliding surface 16. A film 30 is provided. The polymer film 30 is formed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface 16 as in the first embodiment.
The artificial shoulder joint 70 functions as a shoulder joint capable of performing a back-and-forth movement and a turning movement by bringing the head 27 of the humeral stem 25 into contact with the sliding surface 16 of the glenoid cup 15 and sliding it.

  In the shoulder prosthesis 70 of the third embodiment, the sliding surface 16 of the cup base material 17 is provided with the polymer film 30 having a phosphorylcholine group, so that the sliding characteristics of the sliding member are improved and the wear resistance is increased. And durability is improved. Thereby, generation | occurrence | production of an abrasion powder can be suppressed over a long period of time, loosening can be suppressed, and an artificial shoulder joint with few or unnecessary re-replacements can be obtained.

<Embodiment 4>
FIG. 5 shows an artificial spine 32, which is composed of an upper component 33 and a lower component 34 that are respectively fixed to two upper and lower vertebral bodies sandwiching the intervertebral disc.
The lower component 34 protrudes from a lower surface of the case 35, a convex sliding member 36 that secures sliding of the joint portion instead of the intervertebral disc, a metal case 35 that receives the convex sliding member 36, and And a stem 39 for fixing the lower component 34 to the vertebral body.
The convex sliding member 36 includes a disk-shaped substrate 37 having a bulge (sliding surface 16) at the center, and a polymer film 30 coated on the sliding surface 16. The polymer film 30 is formed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface 16 as in the first embodiment.
The upper component 33 is made of metal, and has a concave receiving portion 38 that slidably receives the sliding surface 16 of the convex sliding member 36 on the lower surface, and is fixed to the vertebral body on the upper surface. A stem 39 is provided.
The artificial spine 32 constitutes a part of the spine that can be bent in all directions by bringing the concave receiving portion 38 of the upper component 33 into contact with the sliding surface 16 of the convex sliding member 36 for sliding movement. is doing.

  In the artificial spine 32 of the fourth embodiment, the sliding surface of the convex sliding member 36 of the lower component 34 is provided with the polymer film 30 having a phosphorylcholine group, thereby improving the sliding characteristics of the sliding member. Thus, wear resistance and durability are improved. Thereby, generation | occurrence | production of an abrasion powder can be suppressed over a long period of time, loosening can be suppressed, and the artificial spine with few or unnecessary frequency | counts of replacement can be obtained.

<Embodiments 5 to 8>
FIGS. 6 to 9 are artificial joints for replacing joints that mainly exercise the bending in the front-rear direction. Such an artificial joint can be classified into two types: a hinge type in which two members constituting the joint are coupled by a shaft, and a non-hinge type in which the two members constituting the joint are used in contact.
Currently used hinge type artificial joints include artificial finger joints, artificial knee joints or artificial elbow joints, and non-hinge type artificial joints include artificial knee joints, artificial elbow joints or artificial ankle joints. is there.
Examples of non-hinge type artificial joints and hinge type artificial joints are shown below.

(Embodiment 5)
FIG. 6 shows a non-hinge type knee prosthesis 72, a tibial component 50 fixed to the proximal portion of the tibia, and a metal or ceramic joint member (femoral component) fixed to the distal portion of the femur. 52), which are fixed to each bone end in a separated state.
The femoral component 52 has, on its lower surface side, two curved projecting surfaces 53 and 53 (inner condyles and 53A) extending in an arc from the anterior direction (the kneecap direction, arrow A) to the posterior direction (the back of the knee, arrow P). With lateral condyles).

The tibial component 50 of the knee prosthesis 72 includes a sliding member (tibial tray 48) that constitutes the joint surface, and a tibial stem 51 that fixes the tibial tray 48 to the tibia. The tibial tray 48 has a curved recess formed on the upper surface thereof extending from the front direction A to the rear direction P. The slide surface is in contact with the two projecting surfaces 53, 53 of the femoral component 52. 16 and 16. Specifically, the tibial tray 48 is formed of a tray base material 49 formed from UHMWPE and a polymer film 30 coated on the sliding surfaces 16 and 16 of the tray base material 49. The polymer film 30 is formed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface 16 as in the first embodiment.
The artificial knee joint 72 of the fifth embodiment can bend and stretch in the front-rear direction by sliding the projecting surfaces 53 and 53 of the femoral component 52 and the sliding surfaces 16 and 16 of the tibial tray 48. .

(Embodiment 6)
FIG. 7 shows a non-hinge type artificial elbow joint 74 comprising an ulna component 58 fixed to the proximal portion of the ulna and an articulation member (humeral component 62) fixed to the distal portion of the humerus. These are fixed to each epiphysis in a separated state.
The ulna component 58 includes a sliding member (ulna tray 54) that constitutes the joint surface, and an ulna stem 60 that fixes the ulna tray 54 to the ulna. The ulna tray 54 has a shape obtained by cutting off a part of the annular member in the radial direction, and the inner surface is the sliding surface 16. The sliding surface 16 of the ulna tray 54 swells from the edges on both sides in the width direction toward the central direction, and forms a ridge portion 55 extending in the circumferential direction.
Specifically, the ulna tray 54 is formed of a tray base material 56 formed from UHMWPE and the polymer film 30 coated on the sliding surface 16 of the tray base material 56. The polymer film 30 is formed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface 16 as in the first embodiment.

The humeral component 62 of the artificial elbow joint 74 is formed of metal or ceramics and has a substantially cylindrical shape with a part cut away. The outer surface of the humeral component 62 is slightly constricted in the middle to form a pulley 63.
By fitting the pulley 63 of the humerus component 62 and the protruding portion 55 of the ulna tray 54, an artificial elbow joint that can bend and stretch forward and backward is formed.

(Embodiment 7)
FIG. 8 shows a non-hinge type artificial ankle 76 (for the left foot), a tibial component 66 fixed to the distal portion of the tibia, and a joint member (talar component 68) fixed to the proximal portion of the talus. These are fixed to each bone end in a separated state.
The tibial component 66 includes a sliding member (tibial tray 64) that constitutes an articulating surface, and a tibial stem 67 that fixes the tibial tray 64 to the tibia.
The tibial tray 64 has a lower surface formed into a concave curved surface curved from the front direction A toward the rear direction P, and the lower surface is a sliding surface 16. Further, a flange 96 projects downward from the edge of the inner side M of the tibial tray 64 to prevent the joint from being displaced in the lateral direction. Specifically, the tibial tray 64 is formed of a tray base 65 formed from UHMWPE and the polymer film 30 coated on the sliding surface 16 of the tray base 65. The polymer film 30 is formed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface 16 as in the first embodiment.

The talar component 68 of the artificial ankle 76 is formed of metal or ceramics and has an upper surface formed of a convex curved surface that curves from the front direction A toward the rear direction P. The talar component 68 is also secured to the proximal portion of the talus by inserting a talus stem 98 formed on the underside into the bone marrow of the talus.
When the upper surface of the talar component 68 and the sliding surface 16 of the tibial tray 64 are slidably in contact with each other, an artificial ankle joint that can be bent back and forth is formed.

  In Embodiments 5 to 7, by providing the sliding surface of the tray base material with the polymer film 30 having a phosphorylcholine group, the sliding characteristics of the sliding member are improved, and wear resistance and durability are improved. Improves sex. Thereby, generation | occurrence | production of abrasion powder can be suppressed over a long period of time, loosening can be suppressed, and an artificial joint with a small number of unnecessary replacements or an unnecessary joint can be obtained.

(Embodiment 8)
FIG. 9 shows a hinge-type artificial finger joint 80, which is used for the replacement of the joint between the metacarpal bone and the finger bone and the joint between the finger bones. The artificial finger joint 80 is fixed to the axial component 81 fixed to the epiphysis of the phalange located on the distal side of the joint, and to the metacarpal or phalange epiphysis located on the proximal side of the joint. And a bearing component 85.
The shaft-side component 81 is integrally formed of metal or ceramics, and is fixed to the bone end portion by connecting the shaft portion 82 projecting from both ends 84 and 84 to the vicinity of the center of the shaft portion 82. And a stem 83.

  The bearing component 85 of the artificial finger joint 80 includes a bearing member 86 formed with two bearing holes 88 and 88 for fitting both ends of the shaft portion 82, and a stem 87 for fixing the bearing member 86 to the bone end portion. I have. The inner surface of the bearing hole 88 is a sliding surface 16. Specifically, the bearing member 86 is formed of a bearing base 89 formed from UHMWPE and the polymer film 30 covered with the sliding surface 16 of the bearing hole 88. The polymer film 30 is formed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface 16 as in the first embodiment.

In the artificial finger joint 80, a hinge structure is formed by fitting the end portion 84 of the shaft portion 82 into the bearing hole 88 of the bearing component 85. In this hinge structure, when the shaft portion 82 rotates in the bearing hole 88, an artificial finger joint 80 that can bend and stretch is formed.
In the eighth embodiment, the sliding surface 16 of the bearing hole 88 is provided with the polymer film 30 having a phosphorylcholine group, thereby improving the sliding characteristics of the hinge structure and improving the wear resistance and durability. Yes. Thereby, generation | occurrence | production of an abrasion powder can be suppressed over a long period of time, loosening can be suppressed, and an artificial finger joint with few or unnecessary re-replacements can be obtained.

As an artificial joint model, the acetabular cup 10 for an artificial hip joint shown in FIG. 1 and FIG. 2 was formed, and the hydrophilicity, phosphate index, and durability (period in which abrasion resistance can be maintained) were examined. Samples ag were prepared using CLPE for the cup base 12 of the acetabular cup 10.
Samples b to g coated with the polymer film 30 were produced under the following conditions. Sample a is not coated with the polymer film 30 for comparison.

(Preparation of sample b)
Sample b was produced by the following steps.
Step 1. The cup base 12 of the acetabular cup 10 was immersed in an acetone solution of benzophenone (concentration 10 mg / mL) for 30 seconds, and then immediately lifted to remove the solvent on the surface of the cup base 12.
Step 2. With the cup base 12 immersed in an MPC aqueous solution (monomer concentration 0.5 mol / L, aqueous solution temperature 60 ° C.), the sliding surface 16 of the cup base 12 is irradiated with ultraviolet rays (wavelength 300 to 400 nm) for 25 minutes. Thus, a polymer film (MPC polymer film) 30 grafted to the surface of the sliding surface 16 was formed.
Step 3. The cup base material 12 was taken out from the MPC aqueous solution and thoroughly washed with pure water.

(Preparation of sample c)
In the preparation process of Sample b, the same treatment was performed except that the ultraviolet irradiation time in Step 2 was set to 50 minutes.

(Preparation of sample d)
Of the production steps of sample b, the same treatment was performed except that the ultraviolet irradiation time in step 2 was 90 minutes.

(Preparation of sample e)
In the preparation process of sample b, the same process was performed except that the ultraviolet irradiation time of process 2 was 180 minutes.

(Preparation of sample f)
In the preparation process of sample d, the same treatment was performed except that the monomer concentration of the MPC aqueous solution was changed to 0.25 mol / L.

(Preparation of sample g)
In the preparation process of Sample d, the same treatment was performed except that the monomer concentration of the MPC aqueous solution was set to 1.00 mol / L and the ultraviolet irradiation time in Step 2 was set to 90 minutes.

(Measurement of hydrophilicity and phosphate index)
With respect to the MPC polymer film 30 of each sample, a contact angle with respect to water (an index of hydrophilicity) and a phosphoric acid index were measured. The measurement results are shown in Table 1.

(Durability test)
The acceleration test was performed in an environment where the acetabular cups and artificial bone heads of samples a to g were artificially slid to reproduce the state of use in the human body.
For the acceleration test, a wear test apparatus manufactured by MTS, which can simulate the state in which the hip joint slides while rotating and swinging, was used. FIG. 10 is a schematic side view of the wear test apparatus 100, in which a container 102 for storing a body fluid-like liquid is fixed to a rotary motor 106 in an inclined state (for example, 45 °). At the bottom of the container 102 is a holder 104 for fixing the acetabular cup 10. Above the container 102, a head fixing shaft 108 having a head fixed to the tip is disposed, and a load F is applied downward to the head 22 with the head 22 fitted to the sliding surface 16 of the acetabular cup 10. Can be loaded.

  In the durability test, in order to evaluate the durability of the acetabular cup 10 in a state simulating the living body, during the test, the acetabular cup 10 and the bone head 22 were subjected to 0.1% sodium azide and 20 mM ethylenediamine. It was immersed in 25% bovine serum 110 containing trisodium tetraacetate. A commercially available cobalt chromium alloy (diameter 26 mm) was used for the bone head 22, and the walking state was simulated by the walking condition of Double Peak Paul having two peaks of 183 kgf and 280 kgf in one walking cycle per second. The bovine serum 110 was replaced every 500,000 rotation cycles.

In the acceleration test conducted under the above conditions, the mass of the sample was measured every 500,000 rotation cycles, and the amount of wear was determined by dividing the mass of the sample before the wear test. The results are shown in FIG. 11 and FIG. Graphs ag in the figure are test results of samples ag.
In the graphs of FIGS. 11 and 12, the wear amount may be negative. This is because the MPC polymer film 30 and the cup base material 12 constituting the sample have absorbed the moisture, thereby increasing the weight. In this embodiment, when the wear amount becomes negative (that is, when the weight increases), it is assumed that the wear amount is zero.

FIG. 11 shows test results up to 5 million rotation cycles. Up to 2.5 million rotation cycles, the samples b to g equipped with the MPC polymer film showed no significant increase in the amount of wear and showed good wear resistance. However, when the number of rotation cycles is 3 million times or more, the wear amount of the sample b increases rapidly, and at 4 million times, the wear amount is equal to the wear amount of the sample a (without MPC polymer film). The number of wear was more than the amount of sample a. The sample g was delayed from the sample b, and the amount of wear increased rapidly after 3.5 million rotation cycles. After that, the sample g was worn at the same wear rate as the sample a.
From this result, the acetabular cup provided with the MPC polymer film on the sliding surface shows good wear resistance regardless of the density of the MPC polymer film during a short period of use. It has been found that a low MPC polymer film exhibits no wear resistance. Moreover, although the sample g had a high phosphoric acid index, the durability was lowered because the film thickness of the sample g was thick, so that even if the coating was partially insufficient, the phosphoric acid index was high. This is thought to be because of

  FIG. 12 shows test results for samples a, c, and d up to 10 million rotation cycles. In sample a (without MPC polymer film), the amount of wear increased almost in proportion to the number of rotation cycles. Sample c has an extremely small amount of wear at 8 million revolutions or less and exhibits excellent wear resistance. Sample d showed no significant increase in wear up to 10 million times, and was found to be able to maintain excellent durability and wear resistance unchanged from the beginning of use over a long period of time.

  Among the results of the durability test shown in FIGS. 11 and 12, for samples using solutions having the same monomer concentration: 1. UV irradiation time 2. Contact angle with water, and A summary of the three indices of the phosphoric acid index is shown in FIGS. Points a to e in the figure are test results of samples a to e.

In the graphs of FIGS. 13 to 15, the wear rate (mg / million times) on the vertical axis is the weight (mg) at which the acetabular cup is worn by 1 million rotation cycles. For example, the wear rate at 10 million times is the weight at which the acetabular cup is worn in 1 million times between 9 million times and 10 million times from the start of the test. In the accelerated test, 1 million rotation cycles corresponds to 1 year of use, so the wear rate can be converted to the amount of wear powder generated per year.
In general, a small amount of wear powder is processed by macrophages, but the number of wear powder found in clinical use ranges from tens to millions, far exceeding the physiological capacity of phagocytic cells. It is believed that cytokines released by phagocytic cells (PGE2, TNF-α, IL-1, IL-6, etc.) excessively stimulate osteoclasts and generate osteolysis. That is, it is considered that osteolysis can be effectively suppressed by suppressing the amount of wear powder generated in a certain period to be lower than the allowable processing limit of wear powder in the body. Therefore, it can be said that the wear rate is suitable as an index for knowing the effect of suppressing bone melting.

  In a conventional hip prosthesis, the UHMWPE acetabular cup has a wear rate of 10 to 20 mg / million times, and the CLPE acetabular cup has a wear rate of 3 to 5 mg / million times. In this example, in order to clarify the range in which the wear rate can be suppressed to a very low value, the wear rate of 1 mg / million times or less was used as the reference for wear resistance. The relationship between the suitability of wear resistance at a predetermined number of rotation cycles and the above three indices (ultraviolet irradiation time, contact angle with water, and phosphoric acid index) was examined.

The graph of FIG. 13 shows the wear rate of the cup when a sliding motion (corresponding to use for about 3 years) of 2.5 million rotation cycles was performed. 13A is a graph plotting the wear rate with respect to the polymerization time, FIG. 13B is a graph plotting the wear rate with respect to the contact angle, and FIG. 13C is the wear rate with respect to the phosphate index.
From these graphs, by providing the sliding surface 16 with an MPC polymer film having an ultraviolet irradiation time of 25 minutes or more, a contact angle with water of 50 ° or less, and a phosphoric acid index of 0.15 or more, the acetabular cup 10 is approximately It was found that good wear resistance can be maintained even after 3 years of use. Further, in the 2.5 million tests, the wear rate of the acetabular cup 10 tended to monotonously increase or monotonously decrease with respect to the three indicators of the ultraviolet irradiation time, the contact angle with water, and the phosphoric acid index.

The graph of FIG. 14 shows the wear rate of the cup when a sliding motion (corresponding to use for about 5 years) of 5 million rotation cycles is performed. 14A is a graph plotting the wear rate with respect to the polymerization time, FIG. 14B is a graph plotting the wear rate with respect to the contact angle, and FIG. 14C is a graph plotting the wear rate with respect to the phosphate index.
From this graph, the acetabular cup 10 is subjected to an acceleration experiment by providing the sliding surface 16 with an MPC polymer film having an ultraviolet irradiation time of 45 minutes or more, a water contact angle of 20 ° or less, and a phosphoric acid index of 0.28 or more. From these results, it is estimated that good wear resistance can be maintained even after about 5 years of use.
In the test of 5 million times, unlike the test result of 2.5 million times, the wear rate of sample b (with MPC polymer film having a phosphate index of 0.1) exceeds the wear rate of sample a (without MPC polymer film). It was.

The graph of FIG. 15 shows the wear rate of the cup when a sliding motion (corresponding to use for about 10 years) of 10 million rotation cycles is performed. 15A is a graph plotting the wear rate with respect to the polymerization time, FIG. 15B is a graph plotting the wear rate with respect to the contact angle, and FIG. 15C is the wear rate with respect to the phosphate index.
From this graph, the acetabular cup 10 is subjected to an acceleration experiment by providing the sliding surface 16 with an MPC polymer film having an ultraviolet irradiation time of 90 minutes or more, a contact angle with water of 14 ° or less, and a phosphoric acid index of 0.45 or more. From these results, it is estimated that good wear resistance can be maintained even after about 10 years of use.
In 10 million tests, the wear rate of sample c (with MPC polymer film having a phosphoric acid index of 0.32) was reduced to the same level as that of sample a (without MPC polymer film).

From FIGS. 13 to 14, when the MPC polymer film is formed on the acetabular cup, the wear resistance can be improved regardless of the density of the film up to about 3 years from the start of use. It was revealed that when the density of the polymer film is low, sufficient durability may not be imparted to the acetabular cup.
Further, when compared with the amount of wear generated in an acceleration experiment (5 million times) corresponding to use for about 5 years, the amount of wear of the acetabular cup (samples c to e) using the sliding member of the present invention is MPC. The amount of wear of the uncoated UHMWPE acetabular cup was reduced to about 1/20 or less, and the amount of wear of the MPPE uncoated CLPE acetabular cup (Sample a) was reduced to about 1/10 or less. This indicates that the sliding member of the present invention can withstand long-term clinical use.

(Comparative example)
The wear resistance when a mortar cup (specimen X) was formed under the production conditions disclosed in Patent Document 5 was estimated and plotted as points X in FIGS. The manufacturing process of Sample X was the same as the manufacturing process of Sample b of this example except that the ultraviolet irradiation time in Step 2 was set to 30 minutes.
The wear rate of sample X is within the allowable range at 2.5 million rotation cycles, but is not acceptable at 5 million times, and is estimated to decrease to the same level as sample a without MPC polymer film at 10 million times. The

  Thus, in order to obtain a sliding member having excellent wear resistance over a long period of time, it is not sufficient to provide a polymer film having a phosphorylcholine group on the sliding surface. It became clear that there was a need to raise it.

In order to indirectly know the density of the MPC polymer film existing on the sliding surface for the samples a to e produced in Example 1, the phosphorus atom concentration and the nitrogen atom concentration (atom%) of the sliding surface were measured. Then, the relationship between the atomic concentration and the durability of the sample was investigated.
As can be seen from the chemical structural formula of the MPC monomer, one molecule of MPC monomer contains one phosphorus atom concentration and one nitrogen atom. Therefore, the phosphorus atom concentration and nitrogen atom content (corresponding to the atomic concentration) contained in the measurement region are proportional to the number of MPC monomers in the range. That is, the phosphorus atom concentration and the nitrogen atom atomic concentration can be used as an index for knowing the density of the MPC polymer film.

  X-ray photoelectron spectroscopy (XPS) analysis was used to determine the phosphorus atom concentration and the nitrogen atom concentration. XPS has the advantage that it can be measured even when the sample surface has a concavo-convex shape because the analysis region is extremely small compared to the FT-IR of Example 1. On the other hand, since the measurement result of the XPS analysis reflects only local information, if the MPC polymer film is not completely uniform, the result obtained may vary depending on the measurement location. Therefore, it is preferable to average the measurement results of the XPS analysis from the results measured at a plurality of points.

  For XPS analysis, Mg-Kα ray was used as an X-ray source, and measurement was performed under conditions of an applied voltage of 15 kV and a detection angle of 90 °. Using the obtained XPS spectrum, the atomic concentration of phosphorus atoms and the atomic concentration of nitrogen atoms were determined. The unit of atomic concentration is expressed as atom%.

When XPS analysis was performed on the MPC polymer film formed on the sliding surfaces of the samples a to e prepared in Example 1, the atomic concentrations of phosphorus atoms and nitrogen atoms in the MPC polymer film were as shown in Table 2. .

Based on the results of Table 2 and the results of the abrasion resistance test of Example 1, the relationship between the atomic concentration and the abrasion resistance is shown in FIGS. Points a to e in the figure are test results of samples a to e.
The graph of FIG. 16 has a sliding motion of 2.5 million rotation cycles (corresponding to use of about 3 years), the graph of FIG. 17 has a sliding motion of 5 million rotation cycles (corresponding to use of about 5 years), The graph of FIG. 18 shows the wear rate of the cup when a sliding motion (corresponding to use for about 10 years) of 10 million rotation cycles is performed. FIGS. 16A, 17A, and 18A are graphs plotting the wear rate against the atomic concentration of phosphorus atoms. FIGS. 16B, 17B, and 18B are graphs plotting the wear rate against the atomic concentration of nitrogen atoms.

In the same manner as in Example 1, the threshold value in each rotation cycle was determined using a wear rate of 1 mg / million times or less as a reference for wear resistance.
From the graph of 2.5 million rotation cycles shown in FIG. 16, if the atomic concentration of phosphorus atoms is 3.1 atom% or more and the atomic concentration of nitrogen atoms is 2.3 atom% or more, within a period of use of about 3 years, It was found to show good wear resistance. In addition, at 2.5 million times, the wear resistance tended to improve as the atomic concentration increased.

  From the graph of 5 million rotation cycles shown in FIG. 17, when the atomic concentration of phosphorus atoms is 4.7 atom% or more and the atomic concentration of nitrogen atoms is 3.6 atom% or more, the durability is good and 5 years. It can be estimated that excellent wear resistance is exhibited even after a certain degree of use. Further, from the graph of 10 million rotation cycles shown in FIG. 18, when the atomic concentration of phosphorus atoms is 4.6 atom% or more and the atomic concentration of nitrogen atoms is 3.5 atom% or more, the durability is further improved. It can be estimated that excellent wear resistance is exhibited even after long-term use exceeding 5 years. In addition, the test result of 5 million times or more is different from the test result of 2.5 million times, and wear of sample b (with MPC polymer film having an atomic concentration of 2.65 atom% of phosphorus atoms and an atomic concentration of 1.86 atom% of nitrogen atoms) The rate exceeded the wear rate of sample a (without MPC polymer film).

  16-18, when the MPC polymer film is formed on the acetabular cup, the wear resistance can be improved up to about 3 years from the start of use regardless of the density of the film. It was revealed that when the density of the polymer film is low, sufficient durability may not be imparted to the acetabular cup.

  For the samples a, d, f, and g produced in Example 1, the thickness of the MPC polymer film covering the sliding surface of the acetabular cup was measured. The sample used for the measurement was embedded in an epoxy resin, stained with ruthenium tetrachloride, and then an ultrathin section was cut out using an ultramicrotome. For the observation, an acceleration voltage of 100 kV was used using a JEM-1010 transmission electron microscope (TEM) manufactured by JEOL.

  19A shows sample a without MPC coating, FIG. 19B shows sample f (monomer concentration 0.25 mol / L), FIG. 19C shows sample d (monomer concentration 0.50 mol / L), and FIG. 19D shows sample g (monomer concentration). 1.00 mol / L).

  In FIG. 19B to FIG. 19D, a coating layer (MPC polymer film) that was not seen in FIG. 19A was observed. In FIG. 19B, the film thickness is 10 to 30 nm, and in FIG. 19C, the film thickness is 100 to 200 nm. Observation of a plurality of TEM images confirmed that the MPC polymer film covered the entire sliding surface. On the other hand, in FIG. 19D, an MPC polymer film having a film thickness of 200 to 250 nm is formed, but when observed at a plurality of locations, so-called pinholes in which almost no film is formed are scattered. I found out. This is considered to be due to the following reason.

  By irradiating the sliding surface with ultraviolet light while the acetabular cup is impregnated with the monomer solution, benzophenone on the sliding surface is activated, and subsequently, polyethylene on the sliding surface is activated. The activated polyethylene reacts with the MPC monomer in the monomer solution, and graft polymerizes on the surface of the sliding portion. If graft polymerization at this time is appropriate, the density of the MPC polymer is increased. Then, MPC monomers in the solution are successively polymerized to the MPC polymer polymerized on the sliding surface, and the MPC polymer chain length is increased, resulting in an increase in film thickness. When the monomer concentration of the monomer solution is 0.25 mol / L (sample f) to 0.75 mol / L (sample d), the graft polymerization proceeds appropriately. However, if the monomer concentration of the monomer solution is too high, for example, 1.0 mol / L, the MPC monomer that has received ultraviolet rays starts to polymerize with a nearby MPC monomer before reaching the sliding surface. MPC polymer is formed. Since the MPC polymer is not bonded to the sliding surface, it is removed from the acetabular cup when washed. The formation of this MPC polymer rapidly lowers the surrounding MPC monomer concentration, so that a region where the monomer concentration is locally low is formed. If the monomer concentration is too low, the MPC polymer film cannot be formed, and pinholes are formed. End up.

  Thus, even if the concentration of the MPC monomer solution is too low or too high, a uniform MPC polymer film cannot be formed, leading to a decrease in the durability of the acetabular cup.

  The effect on the physical properties of the MPC polymer film was examined when only the monomer concentration was changed under the conditions of the sample d produced in Example 1.

(Measurement of hydrophilicity)
For a plurality of samples with different monomer concentrations, the contact angle (hydrophilic index) of the MPC polymer film 30 with respect to water was measured, and the results are summarized in FIG. In addition, the code | symbol a, d, f, and g in a figure has shown that it corresponds to the samples a, d, f, and g of Example 1. As can be seen from FIG. 20, the contact angle has a minimum value at a constant monomer concentration (0.25 mol / L to 0.50 mol / L), and when it is out of the range, the contact angle tends to increase.
If the monomer concentration is too low, it is considered that the MPC polymer film has a low density or a thin film thickness. In addition, if the monomer concentration is too high, the MPC polymer film thickness increases, but the pinhole generation rate increases and the density of the MPC polymer film locally decreases, resulting in a larger contact angle. It is done.

(Measurement of phosphorus atom concentration and nitrogen atom concentration)
The XPS analysis was performed on a plurality of samples with different monomer concentrations to measure the phosphorus atom concentration and the nitrogen atom concentration, and the results are summarized in FIG. In addition, the code | symbol a, d, f, and g in a figure has shown that it corresponds to the samples a, d, f, and g of Example 1. FIG. 21 shows that the phosphorus atom concentration (graph P) and the nitrogen atom concentration (graph N) show the same tendency. The phosphorus atom concentration and nitrogen concentration are the highest when the monomer concentration is 0.5 mol / L. In the monomer concentration range of 0.25 mol / L to 0.50 mol / L with good hydrophilicity, the phosphorus atom concentration was 4.3 atom% or higher and the nitrogen concentration was 3.9 atom% or higher.
In addition, when the monomer concentration is 0.75 mol / L or higher, the phosphorus atom concentration and the nitrogen atom concentration are low although the MPC polymer film is thick. This is presumably because the density of the MPC polymer film was lowered due to the influence of pinholes.

  It was examined how the influence of the ultraviolet irradiation time on the MPC polymer film varies depending on the monomer concentration. In this example, the phosphorus atom concentration was measured as an index. The sample is prepared in the same manner as in Example 1. The monomer concentration of the monomer solution was 0.17 mol / L, 0.25 mol / L, and 0.50 mol / L, and samples were prepared by changing the ultraviolet irradiation time. The phosphorus atom concentration was determined from the XPS analysis of each sample and summarized in FIG. The trend of increasing phosphorus atom concentration was almost the same at all monomer concentrations. The phosphorus atom concentration increased almost in proportion to the irradiation time until the ultraviolet irradiation time of 50 minutes, and it became difficult to increase from there. In other words, regardless of the monomer concentration, it is considered that the MPC polymer film is almost formed by 50 minutes of ultraviolet irradiation. In particular, it was confirmed that when the monomer concentration is high, the rate of increase of the phosphorus atom concentration due to ultraviolet irradiation exceeding 50 minutes is lower than when the monomer concentration is low, and it is almost saturated after irradiation time of 50 minutes. It can be said that irradiation for 50 minutes or more is preferable at all monomer concentrations.

It is the schematic of the artificial hip joint concerning Embodiment 1 of this invention. It is a perspective view of the acetabular cup for artificial hip joints concerning Embodiment 1 of this invention. It is the schematic of the bipolar artificial hip joint concerning Embodiment 2 of this invention. It is the schematic of the artificial shoulder joint concerning Embodiment 3 of this invention. It is the schematic of the artificial spine concerning Embodiment 4 of this invention. It is the schematic of the artificial knee joint concerning Embodiment 5 of this invention. It is the schematic of the artificial elbow joint concerning Embodiment 6 of this invention. It is the schematic of the artificial ankle joint concerning Embodiment 7 of this invention. It is the schematic of the artificial finger joint concerning Embodiment 8 of this invention. It is the schematic of the abrasion test apparatus used for the Example of this invention. It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 1 of this invention. It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 1 of this invention. It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 1 of this invention (AC). It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 1 of this invention (AC). It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 1 of this invention (AC). It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 2 of this invention (A, B). It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 2 of this invention (A, B). It is a graph which shows the result of the abrasion test of the acetabular cup concerning Example 2 of this invention (A, B). It is a cross-sectional TEM image of the acetabular cup concerning Example 3 of this invention. It is a cross-sectional TEM image of the acetabular cup concerning Example 3 of this invention. It is a cross-sectional TEM image of the acetabular cup concerning Example 3 of this invention. It is a cross-sectional TEM image of the acetabular cup concerning Example 3 of this invention. It is a graph which shows the measurement result of the contact angle with respect to the water of the acetabular cup concerning Example 4 of this invention. It is a graph which shows the measurement result of the phosphorus atom concentration and nitrogen atom concentration of the acetabular cup concerning Example 4 of this invention. It is a graph which shows the measurement result of the phosphorus atom concentration of the acetabular cup concerning Example 5 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Artificial hip joint, 10 Acetabular cup, 12 Cup base material, 15 Glenoid socket cup, 16 Sliding surface, 20 Femoral stem, 22, 27 Bone head, 30 Polymer membrane, 32 Artificial spine, 33 Upper component, 36 Convex shape Sliding member, 40 bipolar head, 46 liner base, 48 tibial tray, 52 femoral component, 54 ulnar tray, 62 humeral component, 64 tibial tray, 68 talar component, 70 artificial shoulder joint, 72 artificial knee joint, 74 Artificial elbow joint, 76 Artificial ankle joint, 80 Artificial finger joint, 82 Shaft part, 86 Bearing member.

Claims (20)

A low-abrasion sliding member used in a wet environment,
The sliding member includes a base material molded from a polymer material having a methylene group, and a polymer film covering the sliding surface of the base material,
The polymer film is composed of a phosphorylcholine group-containing polymer chain grafted to the sliding surface,
The polymer film has a thickness of 10 to 200 nm;
A sliding member, wherein the sliding surface has a phosphoric acid index (phosphoric acid group peak intensity / methylene group peak intensity in an infrared spectroscopic analysis spectrum) of 0.45 or more.   The sliding member according to claim 1, wherein the polymer film has a thickness of 30 to 100 nm.   The sliding member according to claim 1 or 2, wherein the polymer film having a phosphorylcholine group has a wettability to water of 20 ° or less.   The sliding member according to claim 3, wherein the polymer film having a phosphorylcholine group has a wettability to water of 14 ° or less. The sliding member according to any one of claims 1 to 4 , wherein a phosphorus atom concentration obtained from X-ray photoelectron spectroscopy analysis of the sliding surface is 4.7 atom% or more. Nitrogen concentration obtained from the X-ray photoelectron spectroscopy of the sliding surface, the sliding member according to any one of claims 1 to 5, characterized in that at least 3.6atom%. The sliding member according to any one of claims 1 to 6 , wherein the polymer film is 2-methacryloyloxyethyl phosphorylcholine polymer. Polymeric materials having the methylene group for forming the substrate 3 million g / mol or more sliding according to any one of claims 1 to 7, characterized in that an ultra high molecular weight polyethylene Moving member. 9. The sliding member according to claim 8 , wherein the polymer material having a methylene group is a cross-linked polyethylene obtained by crosslinking the ultrahigh molecular weight polyethylene. The sliding member according to claim 9 , wherein the base material made of a polymer material having a methylene group contains a free radical. A sliding member for an artificial joint, wherein the sliding member is made of a polymer material contained in an artificial hip joint, an artificial shoulder joint, an artificial spine, an artificial knee joint, an artificial elbow joint, an artificial ankle joint, an artificial finger joint, or an artificial intervertebral disc The sliding member according to any one of claims 1 to 10 , wherein the sliding member is any one of the above. An artificial joint comprising: a sliding member for an artificial joint according to claim 11; and an opposing member made of ceramic or metal that slidably contacts the sliding member. The artificial joint is an artificial hip joint, an artificial shoulder joint, or an artificial spine;
The sliding member for the artificial joint is a cup having a spherical sliding surface,
13. The artificial joint according to claim 12 , wherein the facing member is a bone head that is slidably received or abutted on the sliding surface of the cup. The artificial joint is an artificial knee joint, an artificial elbow joint, or an artificial ankle joint;
The sliding member for the artificial joint is a tray having a curved sliding surface,
The artificial joint according to claim 12 , wherein the facing member is a joint member that is slidably brought into contact with a sliding surface of the tray. The artificial joint is an artificial finger joint having a hinge structure, an artificial knee joint, or an artificial elbow joint,
The opposing member is a shaft-side component having a shaft portion projecting at both ends,
The artificial joint according to claim 12 , wherein the sliding member is a bearing member provided with a bearing hole for slidably fitting both ends of the shaft portion. A method for manufacturing the sliding member according to any one of claims 1 to 11 ,
Molding a base material made of a polymer material having a methylene group;
Forming a polymer film on the sliding surface by fixing the polymer chain having a phosphorylcholine group to the sliding surface of the substrate by graft bonding,
The step of forming the polymer film comprises
Applying a photopolymerization initiator to the sliding surface of the substrate;
Irradiating the sliding surface of the substrate with ultraviolet light having an intensity required to excite the photopolymerization initiator while immersed in a solution containing a polymerizable monomer having a phosphorylcholine group,
The manufacturing method of the sliding member characterized by the monomer concentration of the solution containing the said polymerizable monomer being 0.25-0.50 mol / L. The method for producing a sliding member according to claim 16 , wherein the irradiation time of the ultraviolet ray is 45 minutes to 90 minutes in the process of irradiating the ultraviolet ray in the step of forming the polymer film. The method for producing a sliding member according to claim 16 or 17 , further comprising a step of irradiating the sliding surface of the substrate with gamma rays after the step of forming the polymer film. The step of molding the substrate, a polymer material having a pre-the methylene group was irradiated with high-energy radiation, any one of claims 16 to 18, characterized in that a step of processing the shape of the base material The manufacturing method of the sliding member of Claim 1. The manufacturing method further includes a step of preparing the polymer material having the methylene group irradiated with the high energy rays in advance before the step of forming the base material,
The step of preparing the polymer material includes a step of irradiating the polymer material having a methylene group with gamma rays, and a step of heat-treating the polymer material irradiated with the gamma rays at a temperature below its melting point. The manufacturing method of the sliding member of Claim 19 .

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